This invention relates to electrical control apparatuses and more particularly to a method of testing an electric shift control apparatus for a motor vehicle.
Modern day motor vehicles typically include an automatic transmission in which the shifting is done in response to sensed speed and throttle opening parameters. Originally the automatic transmission was shifted between its various shift modes by a shift lever controlled by the operator and connected to a mode select member of the transmission by a cable or other mechanical linkage. More recently it has been proposed to provide an electric shift control apparatus for the automatic transmission wherein operator input to a push-button control unit positioned in the instrument panel of the vehicle is transmitted electrically to a logic unit which in turn transmits a command signal to a power unit positioned on the transmission housing to move the mode select member of the transmission to a position corresponding to the operator input. Electric shift control apparatus of this type are shown for example in U.S. Pat. Nos. 4,790,204, 4,817,471, 4,841,793 and 4,843,901, all assigned to the assignee of the present application. It has also been proposed to provide an electric shift control apparatus for a four wheel drive motor vehicle wherein the shift control apparatus further includes a further power unit positioned on the transfer case of the vehicle and operative in response to signals received from the logic unit to move the transfer case between its various positions. An electric shift control apparatus of this type is disclosed for example in U.S. application Ser. No. 412,007 filed Sept. 25, 1989 and assigned to the assignee of the present application.
Whereas these electric shift control apparatuses offer many advantages as compared to the prior art mechanical linkages, it is imperative for the commercial success of such apparatuses that each unit or component of the electric shift apparatus function reliably and consistently on the motor vehicle and that the total system perform the requested shifting operations in a trouble-free manner over a long vehicle life.